MARY MORTIMER "The True Teacher" and friend of Lucy Parsons, was selected by Catharine Beecher as a role model of the serious-minded, single woman, making a living and conducting her work according to the standards of a professional educator. She was, effectively, the first executive or principal of the school under the Beecher Plan.

Endowed with a gentle nature, and a great classroom teacher, Mortimer led the school from 1850 to 1856. She taught classes by day then had to board students in her home at night. She, and others, gave up their salary when funds ran low. By 1856 she was exhausted by financial instability and the philosophical battles Beecher was having with Trustees and fundraisers. Mortimer resigned in 1856, plagued by ill health, but was called back into service in 1866, after which the Beecher Plan was reinstalled, the faculty developed, and the enrollment flourished.